A variable valve mechanism 90 of a first conventional example (Patent Document 1) shown in FIG. 6 includes a first arm 93 and a second arm 94. The first arm 93 is driven by a first cam 91 to drive a valve 7, and the second arm 94 is driven by a second cam 92. The operating state of the variable valve mechanism 90 is switched to a second state by coupling the second arm 94 to the first arm 93, and is switched to a first state by decoupling the second arm 94 from the first arm 93. The first state is the state where the valve 7 is driven according to the profile of the first cam 91, and the second state is the state where the valve 7 is driven according to the profile of the second cam 92.
A variable valve mechanism 100 of a second conventional example (Patent Document 2) shown in FIGS. 7A and 7B includes a first input arm 103, a second input arm 104, and an output arm 105. The first input arm 103 is driven by a first cam, and the second input arm 104 is driven by a second cam. The output arm 105 is placed between the first input arm 103 and the second input arm 104, and drives a valve when swinging. The operating state of the variable valve mechanism 100 is switched to a first state by coupling only the first input arm 103 out of the first and second input arms 103, 104 to the output arm 105, and is switched to a second state by coupling only the second input arm 104 out of the first and second input arms 103, 104 to the output arm 105. The first state is the state where the valve is driven according to the profile of the first cam, and the second state is the state where the valve is driven according to the profile of the second cam.